This episode explores just what it takes to keep the ‘city in the sky’ airborne and safe between take-off and landing. Once you’re in the air, flying may seem common and uneventful, but behind the scenes there are thousands of hidden processes keeping you safe. As you sit back and relax, an army of people are hard at work making sure you get to your destination.

One key element of this is navigation, and we discover exactly how pilots find their way across thousands of miles of open sky in the dead of night. We reveal the hidden global network of locators known ‘waypoints’ that pilots can follow like a well-marked trail through the air. Once these were physical radio beacons, but today they’re virtual GPS points – yet the fundamental system for finding your way remains unchanged.

Pilots cannot do it alone – and we meet the air traffic controllers responsible for regulating the busiest airspace in the world: the skies over Atlanta, Georgia. On every shift, they hold the lives of thousands of passengers in their hands – even one tiny error could prove catastrophic. At Atlanta’s En-route Flight Center we reveal exactly what is involved in co-ordinating some of the 100,000 flights that cross the globe every day, while avoiding collisions. In the build-up to Thanksgiving, they are busier than at any time of the year.

We also explore the revolution in aircraft construction, looking at how new ‘composite’ materials have enabled the evolution of planes that are lighter and stronger than ever before. We find out how these materials are manufactured, and how they have also helped transform the passenger experience: thanks to composites’ strength, new planes can be put under high pressure, and this extra air helps us passengers feel better in flight.

Use of new materials can bring new threats, and we follow scientists as they conduct a simulated lightning strike in order to learn how lightning is conducted through the new generation of planes. An ingenious engineering solution had to be developed in order to composite planes safe, and we follow tests in a ‘lightning lab’ to find out how it’s done.

And it’s not all about the planes, it’s also about us human beings. Luckily, when we get sick in the air, there’s a hidden airborne medical service available to help. The Medaire facility, in Phoenix Arizona, offers highly trained ER doctors who can remotely diagnose passengers who fall ill at 35,000 feet. From thousands of miles away, they determine what’s wrong and decide whether or not to force a flight to divert. They may have to decide whether a plane should divert for an emergency landing – something that may cost an airline hundreds of thousands of dollars.

The existence of all of these elements help make flying safer than ever before: today it’s far safer than driving by almost any measure. We look at the astonishing attention to detail in aircraft servicing that has helped the industry achieve this remarkable feat.